1. Field of the Invention
The present invention relates to a toner for developing an electrostatic latent image by an electrophotographic method, an electrostatic recording method, and an electrostatic printing method; a method for manufacturing the toner, and a developer for developing an electrostatic latent image.
2. Description of the Related Art
Copiers, printers, facsimiles, and complex machines combining functions of a copier, printer and facsimile, conducting a dry developing method in an electrostatic copying system are used in various fields ranging from office use to personal use. This has led to stronger demand for not only high image quality, but also reduction in size and weight of the device itself, ecological considerations such as resource-saving and recycling capability, and low running cost. To meet such demands, various improvements in image formation methods have been proposed, and research and development on new image formation methods have been considered.
An image formation method currently most widely used is a two-component development method. In this method, only the toner in the developer is consumed, which causes the concentration of the toner in the developer to reduce. Thus, a replenishment toner must be supplied to the developer so that the mixing ratio of the toner and carrier can remain constant. Therefore, the two-component development method has a disadvantage of enlarging the size of the development device.
On the other hand, a one-component development method does not have the above disadvantage, and is advantageous in reducing the size and weight of the device. However, the method has a disadvantage in that developing history easily appears as a development afterimage, rendering it difficult to obtain high image quality.
Generally, in order to reduce the size of a development device, miniaturization of device components is required, and it is particularly important to reduce the diameter and thickness of a photoreceptor and a developer-holding member. However, for example, when the diameter and thickness of the photoreceptor are reduced, the curvature of the photoreceptor becomes large. Thereby, the width of the contacting portion between a cleaning member such as a cleaning blade and the photoreceptor becomes narrow, making cleaning the photoreceptor difficult. When the thickness of the photoreceptor is further reduced, the mechanical strength of the photoreceptor also diminishes. In this case, if the contact pressure of the cleaning member to the photoreceptor is not reduced, the photoreceptor distorts, and uneven pressure occurs. Meanwhile, adhesion of local linear foreign substances and filming on the surface of the photoreceptor occur under a low temperature and low humidity environment. Therefore, when the contact pressure of the cleaning blade to the photoreceptor is reduced, cleaning failure occurs.
On the other hand, as a measure to reduce running costs, less toner consumption by reducing the diameters of the toner particles, and extending the life of the photoreceptor by using a photoreceptor having abrasion resistance have been examined. Various proposals have been suggested for an organic photoreceptor in which an abrasion-resistant layer is disposed as the surface layer and for a photoreceptor mainly made of amorphous silicon to be used as the photoreceptor having abrasion resistance. However, the abrasion resistance of such photoreceptors is extremely good. Therefore, foreign substances, which are removed from the photoreceptor with abrasion of the photoreceptor, undesirably remain on the surface of the photoreceptor. Moreover, when the photoreceptor is used for a long period of time, toner components, products obtained by discharging the photoreceptor, and paper powder adhere to the surface of the photoreceptor, generating black spots, image defects (obscure image and defects similar to those occurring at the time that an image is rubbed) and image voids (missing portions of an image).
Conventionally, it is known that adding abrasive particles to a toner is effective for the problem regarding cleaning (refer to, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 3-174544 and 56021).
However, since these abrasive particles promote abrasion of the photoreceptor surface, the life of the photoreceptor is shortened. When a small-sized thin photoreceptor or a photoreceptor having high abrasion resistance is used, the photoreceptor requires use of a large quantity of abrasive particles or abrasive particles having a large particle diameter and large polishing effect. As a result, not only is the life of the photoreceptor shortened, but other problems also occur, such as image voids, black spots, and linear defects due to surface contamination of the developer-holding member, photoreceptor and intermediate transferring member and scanning of the photoreceptor, reduction of density due to reduction in developer electrostatic charging property, fogging, and in-machine contamination.
Therefore, there is a need for a toner for developing an electrostatic latent image, which toner exhibits a high cleaning property with respect to the photoreceptor under various environments such as low temperature and low humidity, and high temperature and high humidity, and which can maintain high image quality over a long period of time, with no image voids, black spots, linear defects, or density reduction due to reduction in developer electrostatic charging property, fogging, and in-machine contamination; a method for manufacturing the toner, and a developer for developing an electrostatic latent image.